A frequently employed method in bleaching and whitening is to use violet or blue dyes concurrently in order to improve the bleaching and whitening effect. If such a dye is used in conjunction with a fluorescent whitening agent, this can serve two different purposes. On one hand, it is possible to achieve an increase in the degree of whiteness by compensating for the yellowness of the fabric, in which case the white shade produced by the fluorescent whitening agent on the fabric is largely retained. On the other hand, the object can be to effect with the dye in question a change in the shade of the white effect produced by the fluorescent whitening agent on the fabric. It is thus possible to adjust the desired shade of the white effect.
Shading processes of materials such as paper and textile fabrics are known from e.g. DE 3125495.
These disclosed shading processes use a physical mixture of a photocatalyst and a dyestuff, which are not suitable for a regular use in detergent or softener formulations, because the dyestuffs accumulate with every use and after a few uses the fabrics are colored.
Additionally, the use of a mixture of two components always requires the proper ratio of the two components.
To overcome the problem of accumulation WO 2006/024612 suggests a molecular combination of a photocatalyst and a dyestuff. A wide variety of photocatalysts and classes of dyestuffs are disclosed. The specific combinations disclosed in WO 2006/024612, however, have still the disadvantage that a significant accumulation occurs and the dye conjugate is not photo degraded rapidly enough.
Surprisingly it has now been found that when the phthalocyanine is a sulfonated phthalocyanine and the dyestuff bonded thereto is a mono-azo dyestuff linked via a specific linking group, photo degradation becomes rapid enough so that no color formation on the treated fabric occurs, even after repeated treatment. The improved shading process using these compounds has also an improved exhaustion onto the fabrics. The new compounds are also highly efficient photocatalysts by additional light absorption and energy transfer to the phthalocyanine part of the molecule.